diff --git a/config/mt-d30v b/config/mt-d30v
index d34b774b3..f5081aef5 100644
--- a/config/mt-d30v
+++ b/config/mt-d30v
@@ -1,4 +1,4 @@
 # Build libraries optimizing for space, not speed.
 # Turn off warnings about symbols named the same as registers
- CFLAGS_FOR_TARGET = -g -Os -Wa,-C
- CXXFLAGS_FOR_TARGET = -g -Os -Wa,-C
+ CFLAGS_FOR_TARGET += -g -Os -Wa,-C
+ CXXFLAGS_FOR_TARGET += -g -Os -Wa,-C